Methyl-thiophanthraquinones



Patented July 4, 1,950

I QMETKYL-THIOPHRNTHRAQUINONES ne in. see and. wktor F Weinmayr, Pitman,

or; toll}. I. du Pont-ide Nemours & ,Gompany, f wihnington, DeL, a corporation of Delawa e Hoflmwing. ,itpplicationiilanuarym, 1947, $0113! No. 723,668

a Claims. (01. 260-329) 1 This invention relates tomew thiophanthraquinones, and more particularly to the preparation of methyl-substituted thiophanthraquinones of the formula:

wherein one X stands for a methyl group, while h other X stands ior hydrogen.

The term thiophanthraquinond is employed n the naming of this mpound-in view of the original name used by Scholl and gseer, Ann..;39d 13 1 (1912), who designated ilierpoorrespondin unsubstituted hydro arbon compound hionhanthracene.

This invention has t r its object the preparationof new or anic mpounds particul rly suit.- able for intermediates for the, preparation of dyes. .A further object of the invention is to provide a commercially feasibleflprocess for the preparation of these new methyl-substituted thiophanthraquinones.

These new methyl-substituted thiophanthraquinones, in which the methyl group in each case is in the thiophene ring, may be prepared by ring-closing the corresponding (-methyl-2- thenoyl) -obenzoic acid or the (4-methyl-2- thenoyD-o-benzoic acid with condensing agents commonly employed in the ring-closure of benzoyl-o-benzoic acids. The preierred process for the preparation of the compounds of this invention, however, is the ring-closure of the corresponding methyl-substituted (2-thenoyD-o-benzoic acids in nitrobenzene by means of aluminum chloride. As illustrated in the following examples, the methyl-substituted (Z-thenoyD-o-benzoic acid can be ring-closed without isolation when it is formed by condensation of the methylthiophene with phthalic anhydride in nitrobenzone by means of aluminum chloride, as more particularly illustrated in ou co-pending application Serial No. 723,666. The preferred process for the preparation of the compounds of this invention is the condensation of the methyl-thicphene in phthalic anhydride in nitrobenzene and in the presence of aluminum chloride at temperatures of above 50 C., then adding an additional amount of aluminum chloride and raising the temperature to effect ring-closure to the methylthiophanthraquinone.

'2 The following examples are given "to illustrate the invention. The parts used are by weight.

Emample 1 Ten (10) parts of -('5-methyl-2-thenoy1')-0- be-nzoic'acid was added to a solution of 12 parts ofahiminum-chloride in240 parts ofnitrobenzene. The reaction mass was heated to from 130 to 135 C. for about 20 hours, then poured'onto dilute hydrochloric acid and steam distilled to remove the'solvent. It was boiled with dilute sodium hydroxide to remove unreacted (5-methyl-2- thenoyl) -o-benzoic acid, filtered and washed. The insoluble residue was slurried in a warm solutioncontaining 20 parts of sodium hydroxide and 25 par-ts of sodium hydrosulfite in 1000 parts of water. The insoluble product was removed by filtration and the methyl-thiophanthraquinone was precipitated by adding m-nitrobenzene sodium sulfonate to the remaining solution. 3.5 parts of 2-methyl-thiophanthraquinone, melting at from 245 to 250 0., were obtained. After crystallizing it from a mixture of about '75 parts of high .boiling gasoline and 30 parts of benzene per part of crude product,it was obtained melting at from 249 to 250 C.

Example 2 Thirty (30) parts of anhydrous aluminum chloride and 15 parts of phthalic anhydride were dissolved in 120 parts of nitrobenzene and the solution was heated to from to C. A solution of 10 parts of alpha-methylthiophene in 12 parts of nitrobenzene was added at from 75 to 80 C. over a period of about 30 minutes, and the charge was held at that temperature for 1.5 hours. After cooling to 50 C., 62 parts of nitrobenzene andv 28 parts of aluminum chloride were added and the reaction mass was heated to from to C. for about 18 hours. The charge was poured into dilute hydrochloric acid, steam distilled, and the precipitate which had formed was filtered off. After an extraction with alkaline hydrosulfite and oxidation of the solution as described in Example 1, the Z-methyl-thiophanthraquinone was obtained, which, after crystallization from the solvent mixture as in Example 1, had a melting point of from 249 to 250 C.

Example 3 Five (5) parts of (4-methyl-2-thenoyl)-o-benzoic acid were added to a solution of 7.2 parts of anhydrous aluminum chloride in 62 parts of nitrobenzene. The charge was heated to C. for 18 hours, then cooled, poured onto dilute sulfuric acid and steam distilled. The insoluble residue was filtered, washed acid-free, then slurried in a boiling dilute solution of sodium hydroxide in water, filtered hot and washed alkali-free. One (1) part of unreacted (4-methyl-2-thenoyD- o-benzoic -acid was recovered when the aim-me; filtrate was acidified. Upon drying of the caustic insoluble material, 3 parts of crude 2-methylacid is carried out in nitrobenzene with aluminum chloride, illustrating a preferred process for producing these new compounds, it will be obvious to those skilled in the art that this ringclosure may b r effected by other suitable condensingjgagents WhereEjsuli'u midis employed, it isdifficulflto'avoid sulfonation of'the resulting product. Other solvents such as the chlorinated thiophanthraquinone were obtained. It was puri fied by extraction with high boiling gasoline; in;

Soxhlet apparatus, followed by recrystallization from high boiling gasoline. pure 3-methyl-thiophanthraquinone, from 179 to 180 C., were obtained.

Identical results were obtained when the ring- Two (2) parts off melting at closure was carried out at from 130 to 150 C; for

hours.

Example 4 Thirty parts of anhydrous aluminum chloride and 15 parts of phthalic anhydride were dissolved in 120 parts of nitrobenzene and the solution was heated to C. A mixture of 10 parts of beta-methyl-thiophene and 12 parts of nitrobenzene was added at from 80 to C; over a period of 20 minutes. After one hour of heating at from80 -to 90 C., the charge was cooled to 60 C; and 62 parts of nitrobenzene and 28 parts ofaluminum chloride were added, and the reaction mass was heated to from to 0.

for 18 hours!- The charge was then poured into water, steam distilled to remove the nitrobenzene, and extracted at about 70 C. with a solution of 20 parts of sodium hydroxide and 20 parts ofsodium hydrosulfite in 800 parts of Water. Upon oxidation with 20 parts of m-nitrobenzene sodium sulfonate, 3 parts of 3-methyl-thiophanthraquinone were obtained, melting at from 174 to 176 C. For purification the product was distilled and crystallized from about 30 parts of'high boiling gasoline per part of distilled product. methyl-thiophanthraquinone, melting 179 to 180C was obtained.

While in the above examples the ring-c10 of the methyl-substituted (2-thenoyl) -o-benzoic Pure 3- a at fromure benzenes may be employed in place of nitrobengzene as-thereaction medium.

The ring-closure of the methyl-substituted (2- gbenzo idbids is preferably carried out with aluminum chloride at temperatures: time will of course depend upon the temperatures at' which'thereaetion is carried out.

We claim:

1. [Ijhe methyl-thiophanthraquinones of the formula Thomas, Anhydrous 'Alum inum Chlo'ride,"

pages 511,624, 525;"540, 1 541. Reinhold Pub. 00.,

N.IY 1941. I

90 to C. The reaction 

1. THE METHYL-THIOPHANTHRAQUINONES OF THE FORMULA: 